The co-cracking of the petroleum vacuum residue (XVR) with polypropylene (PP), Samla coal (SC) and Calotropis procera (CL) has been carried out in a batch reactor under isothermal conditions at atmospheric pressure. The liquids obtained by co-cracking have been characterized by Fourier transform infrared spectroscopy, high performance liquid chromatography, H-1 nuclear magnetic resonance (NMR), C-13 NMR, gel permeation chromatography (GPC), and inductively coupled argon plasma analyses. It was found that the liquid products obtained from the co-cracking of ternary and quaternary mixtures of the petroleum vacuum residue with polypropylene, coal and C. procera contained less than 1 ppm of Ni and V. The HPLC analyses indicates that the liquids obtained from the cracking of ternary mixture of XVR+PP+CL were mainly aliphatic in nature (saturates content 87.4%). NMR analyses showed that the aromatic carbon contents decreased (15.0%) in the liquid products derived from the co-cracking of quaternary mixtures of XVR+PP+SC+CL compared to their theoretical averages (taking the averages of aromatic carbon contents of the liquids from XVR, PP, SC and CL individually). The overall results indicated that there exists a definite interaction of reactive species when XVR, PP, SC and CL were co-cracked together. (c) 2008 Elsevier Ltd. All rights reserved.